The present invention relates generally to appliance controllers capable of handling a number of different appliance models and, more particularly, to an encoding technique whereby a controller may identify the particular appliance model within which it is installed.
In the manufacture of consumer appliances, such as microwave ovens, it is highly desirable that a single controller, typically microprocessor- or microcontroller-based, be able to handle a variety of different appliance models. Reasons include cost and inventory control. Manufacturing is greatly simplified if only one controller type need be manufactured and stocked, which can then be employed in any model desired. Similarly, subsequent repair is greatly simplified if a service technician can carry with him a single spare controller that will operate in a variety of different models, rather than having to stock or possibly special order a controller for a specific model.
In a given type of appliance such as a microwave oven, the overall control requirements are nearly the same from model to model, but there are a number of differences which require slightly different programming, particularly for certain automatic functions such as "auto cook" , "auto roast" and "auto defrost" . A number of cooking parameters associated with these functions vary somewhat from model to model, depending upon such factors as microwave cooking cavity size. Thus, a controller may be called upon to operate correctly in different microwave oven chassis having cooking cavities of different sizes, such as 0.8 cubic foot, 1.0 cubic foot and 1.4 cubic feet, as well as different configurations. In addition, each chassis may support a number of different models. Some models may be equipped with such features as temperature probes or humidity sensors for the implementation of more complex cooking algorithms, while other, more basic, models are not. Even where different models employ the same overall cooking algorithms, different data sets for different models may be required, particularly where different chassis are represented.
With the nearly universal use of microprocessor-based controllers, typically the only difference in the controller from one oven model to the next is in the programming stored permanently in read only memory (ROM). It is quite feasible for control programs stored permanently in ROM to include the parameters and instructions appropriate for a variety of oven models. Nevertheless, there remains the problem of identifying to the controller the particular model.
One approach would be to provide a part for each controller, such as a particular printed circuit board (PCB) , which is unique to the particular model.
Another approach would be to provide a controller PCB which is modifiable in either the factory or field to encode an identification of the particular model. For example, configuration jumper blocks, other forms of selectable jumpers, or encoding diodes might be provided. One common approach in providing configuration jumpers in general is to initially manufacture a PCB with jumpers or encoding diodes installed in all possible positions such that an installer can simply cut out selected ones to in effect program a particular binary code.
Both of these approaches have drawbacks, however. In either case, extra time is required. Instructions must be provided and maintained, particularly by field service personnel. There is always the possibility of human error, the result of which would not necessarily be readily apparent, since the result may very well be merely a degradation of cooking performance, rather than an obvious failure to work at all.